Epithelial cells are a fundamental component of the body, forming protective linings across various surfaces. Their presence in a urine sample is a common finding during a routine urinalysis, a test used to assess urinary tract health and overall well-being. The detection of these cells does not automatically signal a problem, as a small number of epithelial cells in urine is considered normal.
Epithelial Cells in the Urinary Tract
Epithelial cells line the entire urinary tract, which includes the kidneys, ureters, bladder, and urethra. These cells serve as a protective barrier, separating the internal environment of the body from substances in the urine. They also play roles in absorption, secretion, and filtration. The body naturally sheds old or damaged cells as part of its normal cell turnover process, and a small number of these are routinely found in urine.
Types and Significance in Urine
When epithelial cells are detected in urine, identifying their specific type is important, as it can offer insights into their origin and potential implications. There are three primary types of epithelial cells that may be found in a urine sample: squamous, transitional (urothelial), and renal tubular cells.
Squamous Epithelial Cells
Squamous epithelial cells are the largest type and typically originate from the outer urethra or the external genital area. A small number of squamous cells (around 1 to 5 per high-power field) is generally considered normal. However, an elevated count of these cells usually suggests that the sample was not collected using the proper “clean catch” method, indicating contamination.
Transitional Epithelial Cells
Transitional epithelial cells, also known as urothelial cells, line the bladder, ureters, and the upper part of the urethra. These cells are unique because they can stretch and change shape, allowing the bladder to expand. While a limited number of transitional cells in urine can be normal, an increased amount may suggest inflammation, infection, or irritation within the bladder or other parts of the urinary tract.
Renal Tubular Epithelial Cells (RTECs)
Renal tubular epithelial cells (RTECs) are the smallest and most clinically significant type found in urine, as they originate directly from the kidney tubules. The presence of RTECs in urine can indicate damage or disease within the kidneys. More than 15 renal tubular epithelial cells per high-power field may suggest impaired kidney function or injury to the renal tubules, prompting further investigation.
Common Causes of Elevated Epithelial Cells
An increased presence of epithelial cells in urine can stem from several common medical conditions or other factors. Urinary tract infections (UTIs) are a frequent cause, as bacterial infections lead to inflammation and irritation of the urinary tract lining, causing increased shedding of epithelial cells into the urine. This inflammatory response often results in a higher number of transitional cells.
Kidney disease is another significant cause, particularly for an increase in renal tubular epithelial cells. Conditions such as glomerulonephritis or chronic kidney disease can result in damage to the kidney tubules. Inflammation or injury anywhere along the urinary tract, whether due to trauma, medical procedures like catheterization, or other underlying conditions, can also trigger increased epithelial cell shedding.
Kidney stones can also contribute to elevated epithelial cell counts. As these hard mineral deposits pass through the urinary tract, they can cause irritation and damage to the lining, prompting cells to shed into the urine. Additionally, certain medications, particularly chemotherapy drugs, may lead to an increase in epithelial cells. Improper urine sample collection is a common non-medical reason for elevated squamous epithelial cells.
Diagnosis and Management
When elevated epithelial cells are found in a urine sample, healthcare professionals consider this finding as one piece of a larger diagnostic puzzle. Further evaluation is often necessary to determine the underlying cause. Doctors will typically assess other components of the urinalysis, such as the presence of white blood cells, red blood cells, bacteria, or protein, as these can provide additional clues.
A discussion of the patient’s symptoms, medical history, and recent activities is important. For instance, symptoms like painful urination, frequent urges, or fever can point towards an infection. If a urinary tract infection is suspected, a urine culture may be ordered to identify the specific bacteria and guide antibiotic treatment.
For concerns about kidney health, blood tests measuring kidney function or imaging studies may be recommended. If contamination is suspected, especially with a high number of squamous cells, the doctor might ask for a repeat urine sample collected using stricter “clean catch” instructions. The presence of epithelial cells alone is rarely a definitive diagnosis, and a healthcare provider will integrate all findings to arrive at an accurate assessment and recommend appropriate management.